|Peng, Yun - GANSU AGR. UNIV.|
|Wu, Jian - GANSU AGR. UNIV.|
|Wei, Li - NW INST. PLATEAU BILOGY|
|Wu, Ji - GANSU AGR. UNIV.|
|Sanbei, Duo - HAINAN CANTON CNT. FARM|
Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 5, 2008
Publication Date: October 1, 2008
Citation: Peng, Y.S., Brown, M.A., Wu, J.P., Wei, L.X., Wu, J.L., Sanbei, D.Z. 2008. Fatty acid profile and conjugated linoleic ccid (CLA) in the milk fate from Qingphai yak. Professional Animal Scientist. 24:479-487. Interpretive Summary: Qinghai Plateau yak are the most important grazing livestock for milk and beef production on the Qinghai-Tibetan plateau, are adapted to the extremes of cold environment and high elevation, and can graze throughout the year. The milk and the milk products of yak (Bos grunniens) are major ingredients in the daily diets of Tibetan herders while dairy products from Bos taurus breeds are important dietary components in the U.S. Also, genetic advantages in yak milk fatty acid profiles might benefit to dairy production in the United States, given genes for the improved profiles could be identified and transferred. Consequently, research was conducted to evaluate the fatty acid composition of milk from Qinghai Plateau yak at different elevations and at different cow ages and to compare the milk fatty acid composition of yak with that of Qinghai Yellow beef cattle (Bos taurus). Fatty acid profiles of yak cows were significantly different from that of Qinghai Yellow Cattle cows and the concentration of beneficial fatty acids such as C18:0 in the milk fat of yak cows was significantly greater than that reported from other studies for other grazing dairy cows. Other research has found that conjugated linoleic acid (CLA) has beneficial effects for immune function, atherosclerosis, cancer prevention, diabetes prevention, and prevention and management of obesity. In this research, the fatty acid composition of the diet appeared to be an important factor influencing the conjugated linoleic acid (CLA) concentration of the milk fat which may relate to the differences among plant species growing at different elevations. The CLA concentration in the milk fat was associated with C18:1t11 and C18:2c11,c14, two fatty acids believed to be involved in CLA synthesis. There were differences between older cows and first-calf yak cows in aspects of the fatty acid profile of the milk fat, especially in the concentration of CLA in the milk fat, suggesting that milk from older yak cows has nutritive advantages and may be more desirable for household use compared to milk from first-calf cows.
Technical Abstract: The milk and the milk products of yak (Bos grunniens) are major ingredients in the daily diets of Tibetan herders while dairy products from Bos taurus breeds are important dietary components in the U.S. Also, genetic advantages in yak milk fatty acid profiles might benefit to dairy production in the United States, given the genes for the improved profiles could be identified and transferred. Milk samples (n=47) from Qinghai Plateau yak cows of different parities and milk samples (n=6) from Qinghai Yellow Cattle cows were analyzed for fatty acid composition using GC-mass spectrophotometry. Differences in fatty acid profiles of yak milk fat from rangelands at three different elevations, two parities, and between species were compared. Additionally, fatty acid profiles of forages from the different elevations were analyzed. Fatty acid concentrations in the milk fat of yak from the different rangelands were largely similar, but there were differences (P < 0.05) in individual fatty acids, including conjugated linoleic acid (CLA). There was a close correspondence between CLA concentration in the milk fat and fatty acid composition (C18:2c9,c12 and C18:3c9,c12,c15) of forage plants. Milk from multiparous yak cows showed greater (P < 0.01) concentrations of C18:1 and C18:2, total unsaturated fatty acids, total monounsaturated fatty acids, and total polyunsaturated fatty acids and lesser (P < 0.01) proportions of total saturated fatty acids than primiparous counterparts. Conjugated linoleic acid isomer c9, t11 concentration in milk fat from multiparous cows was greater (P < 0.01) than that from primiparous cows. The study results also suggested that the fatty acid profile of the milk fat was different (P < 0.05) for Qinghai Plateau yak compared to those of Qinghai Yellow Cattle.